Light emitting device, light emitting device package and lighting system

ABSTRACT

Provided are a light emitting device, a method of manufacturing the light emitting device, a light emitting device package, and a lighting system. The light emitting device includes a substrate, a light emitting structure including a first conductive type semiconductor layer, an active layer, and a second conductive type semiconductor layer on the substrate, the light emitting structure exposing a portion of the first conductive type semiconductor layer upward, a light transmissive electrode having a stepped portion on the second conductive type semiconductor layer, a second electrode on the light transmissive electrode, and a first electrode on the exposed first conductive type semiconductor layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims under 35 U.S.C. §119 to Korean PatentApplication No. 10-2010-0039597 Filed Apr. 28, 2010, which is herebyincorporated by reference.

BACKGROUND

Embodiments relate to a light emitting device, a light emitting devicepackage and a lighting system.

A light emitting device (LED) includes a p-n junction diode whichconverts electric energy into light energy. The p-n junction diode ismanufactured by combining Group III elements of the periodic table withgroup V elements of the periodic table. The LED can create variouscolors by adjusting a composition of a compound semiconductor.

According to a related art, there are limitations that a lifetime isshortened and reliability is degraded due to current crowding.

In addition, according to the related art, a current may inversely flowto damage an active layer that is a light emitting region whenelectrostatic discharge (ESD) occurs. For solving this limitation, azener diode may be mounted to a package however, light absorption mayoccur in this case.

SUMMARY

Embodiments provide a light emitting device which can improve currentspreading efficiency and light extraction efficiency, a method ofmanufacturing the light emitting device, a light emitting device packageand a lighting system.

Embodiments also provide a light emitting device which can preventdamage due to electrostatic discharge (EDS) without a loss of lightabsorption, a method of manufacturing the light emitting device, a lightemitting device package and a lighting system.

In one embodiment, a light emitting device includes: a substrate; alight emitting structure comprising a first conductive typesemiconductor layer, an active layer, and a second conductive typesemiconductor layer on the substrate, the light emitting structureexposing a portion of the first conductive type semiconductor layerupward; a light transmissive electrode having a stepped portion on thesecond conductive type semiconductor layer; a second electrode on thelight transmissive and a first electrode the exposed first conductivetype semiconductor layer.

In another embodiment, a light emitting device package includes: apackage body; a light emitting device on the package body; and anelectrode electrically connecting the package body to the light emittingdevice.

In further another embodiment, a light emitting module includes thelight emitting device package.

The details of one or more embodiments are set forth in the accompanyingdrawings and the description below. Other features will be apparent fromthe description and drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a light emitting device according to afirst embodiment.

FIGS. 2 to 4 are sectional views illustrating a process of manufacturingthe light emitting device according to the first embodiment.

FIG. 5 is a sectional view of a light emitting device according to asecond embodiment.

FIG. 6 is a concept diagram illustrating an electric field generatedwhen electrostatic discharge occurs in the light emitting deviceaccording to the second embodiment.

FIG. 7 is an exemplary circuit diagram of the light emitting deviceaccording to the second embodiment.

FIG. 8 is a view illustrating a waveform when the electrostaticdischarge occurs in the light emitting device according to the secondembodiment.

FIG. 9 is a sectional view of a light emitting device package accordingto an embodiment.

FIG. 10 is a perspective view of a lighting unit according to anembodiment.

FIG. 11 is an exploded perspective view of a backlight unit according toan embodiment.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, a light emitting device, a light emitting device packageand a lighting system according to embodiments will be described withreference to the accompanying drawings.

In the description of embodiments, it will be understood that when alayer (or film) is referred to as being ‘on’ another layer or substrate,it can be directly on another layer or substrate, or intervening layersmay also be present. Further, it will be understood that when a layer isreferred to as being ‘under’ another layer, it can be directly underanother layer, and one or more intervening layers may also be present.In addition, it will also be understood that when a layer is referred toas being ‘between’ two layers, it can be the only layer between the twolayers, or one or more intervening layers may also be present.

Embodiments

FIG. 1 is a sectional view of a light emitting device according to afirst embodiment.

A light emitting device 100 according to an embodiment may include asubstrate 105, a first conductive type semiconductor layer 112 on thesubstrate 105, an active layer 114, and a second conductive typesemiconductor layer 116. The light emitting device 100 may furtherinclude a light emitting structure 110 upwardly exposing a portion ofthe first conductive type semiconductor layer 112, a light transmissiveelectrode 120 having a stepped portion on the second conductive typesemiconductor layer 116, a second electrode 146 on the lighttransmissive electrode 120, and a first electrode 142 on the exposedfirst conductive type semiconductor layer 112.

According to the embodiment, the light transmissive electrode 120 mayhave a gradually decreasing thickness t in a mesa etching region. Also,according to the embodiment, the light transmissive electrode 120 mayhave a thickness gradually decreasing toward the mesa etching region.Also, the light transmissive electrode 120 has the stepped portionbetween the second electrode 146 and the first electrode 142 and athickness gradually decreasing from the second electrode 146 to thefirst electrode 142.

For example, the light emitting device 100 according to the embodimenthas a structure in which a current spreading property is improved toenhance light emitting efficiency. Also, the light transmissiveelectrode 120 may have thicknesses t different from each other.

For example, in a region of the light transmissive electrode 120 havinga thin thickness, a resistance may be increased to decrease an intensityof a current. On the other hand, in a region of the light transmissiveelectrode 120 having a thick thickness, an intensity of a current may beincreased. Thus, the thickness of the light transmissive electrode 120may be reduced in a mesa edge region to increase the resistance. As aresult, an intensity of a concentrately flowing current may be decreasedso that a uniform current flows into the whole chip region.

In the light emitting device 100 according to the embodiment, thecurrent flow may be efficiently adjusted to increase light extractionefficiency.

Also, according to the embodiment, reliability of the light emittingdevice may be improved through the current spreading property.

Hereinafter, a method of manufacturing the light emitting deviceaccording to the embodiment will be described with reference to FIGS. 2to 4. The light emitting device according to the embodiment may beformed of a group III-V semi conductor material such as GaN, GaAs,GaAsP, or GaP, but is not limited thereto. Also, the present disclosureis not limited to a particular process order described below. Forexample, the process order may be changed.

Referring to FIG. 2, a substrate 105 is prepared. The substrate 105 mayinclude a conductive or insulating substrate. For example, at least oneof at least one of sapphire (Al₂O₃), SiC, Si, GaAs, GaN, ZnO, Si, GaP,InP, Ge, and Ga₂O₃ may be used as the first substrate 105. An unevenstructure may be formed on the first substrate 105, but is not limitedthereto.

A wet cleaning process may be performed on the substrate 105 to removeimpurities on a surface of the substrate 105.

Thereafter, a light emitting structure 110 including a first conductivetype semiconductor layer 112, an active layer 114, and a secondconductive type semiconductor layer 116 is formed on the substrate 105.

According to the embodiment, an undoped semiconductor layer (not shown)may be formed on the substrate 105. The first conductive typesemiconductor layer 112 may be formed on the undoped semiconductorlayer. For example, an undoped GaN layer may be formed on the substrate105. Then, an n-type GaN layer may be formed on the undoped GaN layer toform the first conductive type semiconductor layer 112.

Also, a buffer layer (not shown) may be formed on the substrate 105. Thebuffer layer may reduce lattice mismatching between a material of thelight emitting structure 110 and the substrate 115. The buffer layer maybe formed of a group III-V compound semiconductor, e.g., at least one ofGaN, InN, AlN, InGaN, AlGaN, InAlGaN, and AlInN. The undopedsemiconductor layer may be formed on the buffer layer, but is notlimited thereto.

The first conductive type semiconductor layer 112 may be realized by agroup III-V compound semiconductor doped with a first conductive dopant.In a case where the first conductive type semiconductor layer 112 is anN-type semiconductor layer, the first conductive dopant may include Si,Ge, Sn, Se, and Te as the N-type dopant, but is not limited thereto.

The first conductive type semiconductor layer 112 may be formed of asemiconductor material having a composition formula ofIn_(x)Al_(y)Ga_(1-x-y)N (0≦x≦1, 0≦y≦1, 0≦x+y≦1), but is not limitedthereto.

The first conductive type semiconductor layer 112 may be formed of atleast one of GaN, InN, AlN, InGaN, AlGaN, InAlGaN, AlInN, AlGaAs,InGaAs, AlInGaAs, GaP, AlGaP, InGaP, AlInGaP, and InP.

In the first conductive type semiconductor layer 112, an N-type GaNlayer may be formed using a method of a chemical vapor deposition (CVD),a molecular beam epitaxy (MBE), a sputtering, or a hydride vapor phaseepitaxy (HVPE). Also, the first conductive type semiconductor layer 112may be formed by injecting a trimethyl gallium gas (TMGa), an ammoniumgas (NH₃), a nitrogen gas (N₂), and a silane gas (SiH₄) including ann-type impurity such as silicon (Si) into a chamber.

The active layer 114 is a layer which emits light having energydetermined by an intrinsic energy band of an active layer (lightemitting layer) material when electrons injected from the firstconductive type semiconductor layer 112 meet holes injected to from thesecond conductive semiconductor layer 116.

The active layer 114 may have at least one of a single quantum wellstructure, a multi quantum well (MQW) structure, a quantum wirestructure, and a quantum dot structure. For example, the active layer114 may have the MQW structure by injecting the trimethyl gallium gas(TMGa), the ammonia gas (NH₂), the nitrogen gas (N₂), and the trimethylindium gas (TMIn), but is not limited thereto.

The well layer/barrier layer of the active layer 114 may have at leastone pair structure of InGaN/GaN, InGaN/InGaN, GaN/AlGaN, InAlGaN/GaN,GaAs(InGaAss)/AlGaAs, and GaP(InGaP)/AlGaP, but is not limited thereto.The well layer may be formed of a material having a band gap less thanthat of the barrier layer.

A conductive clad layer may be formed on or/and under the active layer114. The conductive clad layer may be formed of an AlGaN-basedsemiconductor and have a band gap greater than that of the active layer114.

The second conductive type semiconductor layer 116 may be formed of agroup III-V compound semiconductor doped with a second conductivedopant, e.g., a semi conductor material having a composition formula ofIn_(x)Al_(y)Ga_(1-x-y)N (0≦x≦1, 0≦y≦1, 0≦x+y≦1). For example, the secondconductive type semiconductor layer 116 may be formed of one of GaN,AlN, AlGaN, InGaN, InN, InAlGaN, AlInN, AlGaAs, GaP, GaAs, GaAsP, andAlGaInP. In a case where the second conductive type semiconductor layer116 is a P-type semiconductor layer, the second conductive dopant mayinclude Mg, Zn, Ca, Sr, and Ba as the P-type dopant. The secondconductive type semiconductor layer 116 may be formed in a single layeror multi layer, but is not limited thereto.

In the second conductive type semiconductor layer 116, a P-type GaNlayer may be formed by injecting biscetyl cyclopentadienyl magnesium(EtCp₂Mg){Mg(C₂H₅C₅H₄)₂} including P-type impurities such as thetrimethyl gallium gas (TMGa), the ammonia gas (NH₃), the nitrogen gas(N₂), and magnesium (Mg) into the chamber, but it is not limitedthereto.

In the embodiment, the first conductive type semiconductor layer 112 andthe second conductive type semiconductor layer 116 may be respectivelyrealized as the N-type semiconductor layer and the P-type semiconductorlayer, but are not limited thereto. Furthermore, a semiconductor havinga polarity opposite to that of the second conductive type, e.g., anN-type semiconductor layer (not shown) may be formed on the secondconductive type, semiconductor layer 116. Thus, the light emittingstructure 110 may have one of an N-P junction structure, a P-N junctionstructure, an N-P-N junction structure, and a P-N-P junction structure.

A mesa etching process may be performed on the light emitting structure110 to upwardly expose a portion of the first conductive typesemiconductor layer 112. For example, an etching process may beperformed from the second conductive type semiconductor layer 116 usinga predetermined etching pattern (not shown) as a mask in a region inwhich the first electrode 142 is formed, and then the active layer 114may be successively etched to expose a portion of a top surface of thefirst conductive type semiconductor layer 112.

Referring to FIG. 3, a light transmissive electrode 120 may be formed onthe light emitting structure 110. For example, the light transmissiveelectrode 120 may be formed by multiply stacking a single metal, a metalalloy, or a metal oxide. For example, the light transmissive electrode120 may be formed of at least one of indium tin oxide (ITO), indium zincoxide (IZO), indium zinc tin oxide (IZTO), indium aluminum zinc oxide(IAZO), indium gallium zinc oxide (IGZO), indium gallium tin oxide(IGTO), aluminum zinc oxide (AZO), antimony tin oxide (ATO), galliumzinc oxide (GZO), IZO nitride (IZON), Al—GaZnO(AGZO), ZnO, IrOx, RuOx,NiO, RuOx/ITO, Ni/IrOx/Au, Ni/IrOx/Au/ITO, Ag, Ni, Cr, Ti, Al, Rh, Pd,Ir, Ru, Mg, Zn, Pt, Au, and Hf, but is not limited thereto.

A plurality of etching processes may be performed so that the resultantlight transmissive electrode 120 has thicknesses different from eachother to form the light transmissive electrode 120 having the stoppedportion, but is not limited thereto.

Referring to FIG. 4, a first electrode 142 may be formed on the exposedfirst conductive type semiconductor layer 112, and a second electrode146 may be formed on the light transmissive electrode 120.

The first electrode 142 and the second electrode 146 may be formed of atleast one of Ti, Cr, Ni, Al, Pt, Au, and N, but is not limited thereto.

According to the embodiment, the light transmissive electrode 120 mayhave a gradually decreasing thickness t in a mesa etching region. Forexample, in a region of the light transmissive electrode 120 having athin thickness, a resistance may be increased to decrease an intensityof a current. On the other hand, in a region of the light transmissiveelectrode 120 having a thick thickness, an intensity of a current may beincreased. Thus, the thickness of the light transmissive electrode 120may be reduced in a mesa edge region to increase the resistance. As aresult, an intensity of a concentrately flowing current may be decreasedso that a uniform current flows into the whole chip region.

In the light emitting device 100 according to the embodiment, thecurrent flow may be efficiently adjusted to increase light extractionefficiency.

Also, according to the embodiment, reliability of the light emittingdevice may be improved through the current spreading property.

FIG. 5 is a sectional view of a light emitting device according to asecond embodiment.

The second embodiment may adopt technical features of the firstembodiment.

According to the second embodiment, a dielectric layer 150 may befurther disposed on a light transmissive electrode 120 having a steppedportion. A first electrode 142 may contact a side of the dielectriclayer 150.

Also, the dielectric layer 150 may be disposed on an exposed firstconductive type semiconductor layer 112 and the light transmissiveelectrode 120.

The dielectric layer 150 may be a light transmissive dielectric, andthus disposed on a light emitting region. For example, the dielectriclayer 150 may be formed of TiO₂, Al₂O₃, or SiO₂, but is not limitedthereto.

In the embodiment, the dielectric layer 150 may be disposed in a mesaedge region to prevent a current from being concentrated into the mesaedge region and electrostatic discharge (EDS) from occurring.

Thereafter, the first electrode 142 may be disposed on the exposed firstconductive type semiconductor layer 112 contacting the dielectric layer150. Also, a second electrode 146 may be disposed on the lighttransmissive electrode 120.

According to the second embodiment, the first electrode 142, thedielectric layer 150, and the second electrode 146 may function as ametal/insulator/semiconductor (MIS) capacitor.

According to the embodiment, for preventing a light emitting diode (LED)from being damaged due to the ESD, the dielectric layer 150 may bedisposed between the first electrode 142 and the second electrode 146 torealize a structure in which the first electrode 142 and the secondelectrode 146 are electrically opened.

Thus, although a current flows into an active region under a constantvoltage to generate light, energy having a high frequency component maypass through the dielectric layer when an ESD shock of a pulse form isgenerated due to the ESD to protect an active layer.

According to the second embodiment, the dielectric layer 150 may bedisposed in a mesa edge region to prevent a current from beingconcentrated into the mesa edge region and electrostatic discharge (EDS)from occurring.

The first electrode 142 may be disposed on the exposed first conductivetype semiconductor layer 112, wherein the first electrode 142 maycontact the dielectric layer 150 and extends up to a top surface of thedielectric layer 150.

Thus, a contact area between the first electrode 142 and the dielectriclayer 150 may be increased to increase capacity. In addition, thedielectric layer 150 may firmly contact a light emitting structure bythe first electrode 142.

Also, the dielectric layer 150 may contact the second electrode 146.Also, the second electrode 146 may contact the dielectric layer 150 andalso be disposed on a top surface of the dielectric layer 150 toincrease the capacity and firmly contact the dielectric layer 150.

Also, the dielectric layer 150 may contact the second electrode 146,wherein the dielectric layer 150 may be disposed on a top surface of thesecond electrode 146 to increase the capacity.

According to the embodiment, since the dielectric layer 150 is disposedon the light emitting region, the dielectric layer 150 may be a lighttransmissive dielectric layer, but is not limited thereto.

According to the embodiment, the dielectric layer 150 may contacts thelight transmissive electrode 120. However, the dielectric layer 150 maynot contact the second electrode 146. In this case, since the dielectriclayer 150 covers a small area of a second conductive type semiconductorlayer 116 that is a light extraction region, the EDS prevention effectand the light extraction efficiency may be improved.

According to the embodiment, for preventing the LED from being damageddue to the ESD, the dielectric layer 150 may be disposed between thefirst electrode 142 and the second electrode. Thus, although a currentflows into the active region under a constant voltage to generate light,energy having a high frequency component may pass through the dielectriclayer when an ESD shock of a pulse form is generated due to the ESD toprotect the active layer.

FIG. 6 is a concept diagram illustrating an electric field generatedwhen electrostatic discharge occurs in the light emitting deviceaccording to the second embodiment.

The LED breakdown due to the ESD may occur when a reverse voltage isapplied to the semiconductor. When the reverse voltage is applied, astrong electric field may be induced within the LED active region by acharged electrical charge.

When the ESD occurs, carriers (electrons and holes) are accelerated tocollide with atoms, thereby generate other carriers. Also, the generatedcarriers may generate a large amount of carriers. This phenomenon mayrefer to as avalanche breakdown. If a strong electric field is inducedby the charged electrical charge to apply unbearable static electricityto the semiconductor, the LED semiconductor breakdown may occur due tothe avalanche breakdown.

Thus, as shown in FIG. 6, a capacitor structure having an MIS form maybe inserted so that the electric field loaded to the inside of the LEDactive layer is partially induced to the MIS capacitor to reduce theelectric field of the active region, thereby improving a tolerance tothe ESD.

That is, according to a related art, the whole strong electric field Q₀due to a charged electric charge may be induced into an LED activeregion so that the LED breakdown occurs by the avalanche breakdown. Onthe other hand, according to the embodiment, a portion Q₂ of theelectric field Q₀ due to the charged electric charge may be induced intothe region of the dielectric layer 150 to reduce intensity Q₁ of theelectric field in the LED active region.

FIG. 7 is an exemplary circuit diagram of the light emitting deviceaccording to the second embodiment.

In the embodiment, each of the first dielectric layer 142, thedielectric layer 150, and the second electrode 146 may function as acapacitor C_(D).

As shown in FIG. 7, a circuit for the light emitting device according tothe embodiment may be realized. In a case where a voltage is forwardlyapplied due to a constant voltage, a current flows through the LED togenerate light. Also, in a case where a voltage is reversely applied dueto the ESD, a current flows through the MIS capacitor C_(D).

Here, in a case where a voltage is reversely applied due to the ESD, themore a total capacitance C_(Tot) becomes larger, the more the currentflow to the active layer due to an ESD stress becomes less to reduce theshock.

This relation is expressed as following equations.Q _(Dis) =C _(ESD) V _(ESD)

Where, Q_(Dis) denotes a charge amount during the discharging, C_(ESD)denotes a capacitance during the discharging.C _(Tot) ′=C _(Diode) +C _(D) (with MIS capacitor)C _(Tot) =C _(Diode) (without MIS capacitor)I=dQ/dt=ΔQ/τ=Q _(Dis)/(RC _(Tot))∴C _(Tot) ↑→I↓∴I′=Q _(Dis)/(RC′)<I=Q _(Dis)/(RC _(Tot))

That is, in the case where the voltage is reversely applied due to theESD, the more the total capacitance C_(Tot) becomes larger, the more thecurrent (I′) flown to the active layer due to the ESD stress becomessmaller to reduce the shock.

FIG. 8 is a view illustrating a waveform when the electrostaticdischarge occurs in the light emitting device according to the secondembodiment.

As shown in FIG. 8, a pulse wave has a high frequency component througha Fourier conversion. The more a rising time (t_(r)) becomes steeper,the more the high frequency component becomes larger.

As expressed in following equations, as a frequency becomes higher,impedance (resistance) due to capacitance becomes smaller. Accordingly,in the case where the voltage is reversely applied due to the ESD, sincethe impedance of the MIS capacitor becomes smaller, the high frequencycurrent may flow into the MIS capacitor.

Impedance: Z=Z_(R)+jZ_(Im) (Zr denotes real impedance, j denotes animaginary number factor, and Z_(Im) denotes an impedance due to thecapacitor)

Capacitor: Z_(Im,C)=1/(jωC) (ω=2πf)

That is, in the case where the voltage is reversely applied due to theESD, since the impedance of the MIS capacitor becomes smaller, the highfrequency current may flow into the MIS capacitor.

A method of manufacturing the light emitting device, a light emittingdevice package, and a lighting system according to the embodiment, theLED damage duo to the ESD may be prevented without a loss of lightabsorption.

Also, according to the embodiment, since the capacitor is disposedwithin an LED chip to prevent the LED from being damaged due to the ESD,packaging costs and processes may be simplified, and also, the reductionof light absorption may be minimized.

Also, in the light emitting device 100 according to the embodiment, thecurrent flow may be efficiently adjusted to increase light extractionefficiency.

Also, according to the embodiment, reliability of the light emittingdevice may be improved through the current spreading property.

FIG. 9 is a sectional view of a light emitting device package accordingto an embodiment.

Referring to FIG. 9, a light emitting device package according to anembodiment includes a body part 205, a fourth electrode layer 210 andfifth electrode layer 220 disposed on the body part 205, a lightemitting device 100 disposed on the body part 205 and electricallyconnected to the fourth electrode layer 210 and the fifth electrodelayer 220, and a molding member 240 surrounding the light emittingdevice 100.

The body part 205 may be formed of a silicon material, a syntheticresins material, or a metal material. Also, an inclined surface may bedisposed around the light emitting device 100.

The fourth electrode layer 210 and the fifth electrode layer 220 areelectrically separated from each other and provide a power to the lightemitting device 100. Also, the fourth electrode layer 210 and the fifthelectrode layer 220 may reflect light generated in the light emittingdevice 100 to increase light efficiency. In addition, the fourthelectrode layer 210 and the fifth electrode layer 220 may emit heatgenerated in the light emitting device 100 to the outside.

A vertical type light emitting device illustrated in FIGS. 1 to 5 may beadopted for the light emitting device 100, but is not limited thereto.The light emitting device 100 may be disposed on the body part 205.

The light emitting device 100 may be electrically connected to thefourth electrode layer 210 and/or the fifth electrode layer 220 througha wire 230. In the embodiment, since the vertical type light emittingdevice is described as an example, two wires 230 may be provided.Alternatively, when a flip chip type light emitting device is used asthe light emitting device 100, the wire 230 may not be provided.

The molding member 40 may surround the light emitting device 100 toprotect the light emitting device 100. Also, the molding member 240 maycontain a phosphor to vary a wavelength of light emitted from the lightemitting device 100.

The light emitting device package according to an embodiment may beapplied to a lighting system. The lighting system may include a lightingunit illustrated in FIG. 10 and a backlight unit illustrated in FIG. 11.For example, the lighting system may include traffic lights, vehicleheadlights, and signs.

FIG. 10 is a perspective view of a lighting unit 1100 according to anembodiment.

Referring to FIG. 10, the lighting unit 1100 may include a case body1110, a light emitting module 1130 disposed on the case body 1110, and aconnection terminal 1120 disposed on the case body 1110 to receive apower from an external power source.

The case body 1110 may be formed of a material having an excellent heatradiation characteristic. For example, the case body 1110 may be formedof a metal material or resin material.

The light emitting module 1130 may include a board 1132 and at least onelight emitting device package 200 mounted on the board 1132.

The board 1132 may be an insulator on which circuit patterns areprinted. For example, the board 1132 may include a general printedcircuit board (general PCB), a metal core PCB, a flexible PCB, and aceramic PCB.

The board 1132 may also be formed of a material which efficientlyreflects light, or its surface may be coated with color, e.g., a whiteor silver color, which efficiently reflects light.

At least one light emitting device package 200 may be mounted on theboard 1132. Each of light emitting device packages 200 may include atleast one light emitting diode (LED) 100. The LED 100 may include acolored light emitting diode which emits light having various colorssuch as red, green, blue, or white color or a UV light emitting diodewhich emits ultraviolet rays (UV).

The light emitting module 1130 may include a plurality of light emittingdevice packages 200 to obtain various colors and brightness. Forexample, a white light emitting device, a red light emitting device, anda green light emitting device may be disposed in combination with eachother to secure a high color rendering index (CRT).

The connection terminal 1120 may be electrically connected to the lightemitting module 1130 to supply a power. As shown in FIG. 10, althoughthe connection terminal 1120 is screw-inserted into an external powersource in a socket manner, the present disclosure is not limitedthereto. For example, the connection terminal 1120 may have a pin shape.Thus, the connection terminal 1120 may be inserted into the externalpower source or connected to the external power source using aninterconnection.

FIG. 11 is an exploded perspective view of a backlight unit 1200according to an embodiment.

A backlight unit 1200 according to an embodiment may include a lightguide plate 1210, a light emitting module 1240, a reflective member1220, and a bottom cover 1230, but is not limited thereto. The lightemitting module 1240 may provide light to the light guide plate 1210.The reflective member 1220 may be disposed below the light guide plate1210. The bottom cover 1230 may receive the light guide plate 1210, thelight emitting module 1240, and the reflective member 1220.

The light guide plate 1210 diffuses light to produce planar light. Thelight guide plate 1210 may be formed of a light transmissive material.For example, the light guide plate 1210 may be formed of one of anacrylic resin-based material such as polymethylmethacrylate (PMMA), apolyethylene terephthalate (PET) resin, a poly carbonate (PC) resin, acyclic olefin copolymer (COC) resin, and a polyethylene naphthalate(PEN) resin.

The light emitting module 1240 provides light to at least one surface ofthe light guide plate 1210. Thus, the light emitting module 1240 may beused as a light source of a display device including the backlight unit.

The light emitting module 1240 may contact the light guide plate 1210,but is not limited thereto. Particularly, the light emitting module 1240may include a board 1242 and a plurality of light emitting devicepackages 200 mounted on the board 1242. The board 1242 may contact thelight guide plate 1210, but is not limited thereto.

The board 1242 may be a PCB including a circuit pattern (not shown).However, the board 1242 may include a metal core PCB or a flexible PCBas well as the PCB, but is not limited thereto.

The light emitting device packages 200 may have light emitting surfacesthat emit light on the board 1242 and are spaced a predetermineddistance from the light guide plate 1210.

The reflective member 1220 may be disposed below the light guide plate1210. The reflective member 1220 reflects light incident onto a bottomsurface of the light guide plate 1210 to proceed in an upward direction,thereby improving brightness of the backlight unit. For example, thereflective member may be formed of one of PET, PC, and PVC, but is notlimited thereto.

The bottom cover 1230 may receive the light guide plate 1210, the lightemitting module 1240, and the reflective member 1220. For this, thebottom cover 1230 may have a box shape with an open upper side, but isnot limited thereto.

The bottom cover 1230 may be formed of a metal material or a resinmaterial. Also, the bottom cover 1230 may be manufactured using a pressforming process or an extrusion molding process.

Any reference in this specification to “one embodiment,” “anembodiment,” “example embodiment,” etc., means that a particularfeature, structure, or characteristic described in connection with theembodiment is included in at least one embodiment of the invention. Theappearances of such phrases in various places in the specification arenot necessarily all referring to the same embodiment. Further, when aparticular feature, structure, or characteristic is described inconnection with any embodiment, it is submitted that it is within thepurview of one skilled in the art to effect such feature, structure, orcharacteristic in connection with other ones of the embodiments.

Although embodiments have been described with reference to a number ofillustrative embodiments thereof, it should be understood that numerousother modifications and embodiments can be devised by those skilled inthe art that will fall within the spirit and scope of the principles ofthis disclosure. More particularly, various variations and modificationsare possible in the component parts and/or arrangements of the subjectcombination arrangement within the scope of the disclosure, the drawingsand the appended claims. In addition to variations and modifications inthe component parts and/or arrangements, alternative uses will also beapparent to those skilled in the art.

What is claimed is:
 1. A light emitting device comprising: a substrate;a light emitting structure comprising a first conductive typesemiconductor layer, an active layer, and a second conductive typesemiconductor layer on the substrate, the light emitting structureexposing a portion of the first conductive type semiconductor layerupward; a light transmissive electrode having a stepped portion on thesecond conductive type semiconductor layer; a second electrode on thelight transmissive electrode; and a first electrode on the exposed firstconductive type semiconductor layer, wherein the light transmissiveelectrode has a thickness gradually decreasing toward a mesa etchingregion.
 2. The light emitting device according to claim 1, wherein thelight transmissive electrode has a gradually decreasing thickness on themesa etching region.
 3. The light emitting device according to claim 1,wherein the light transmissive electrode has the stepped portion betweenthe second electrode and the first electrode, and the light transmissiveelectrode has a thickness gradually decreasing from the second electrodetoward the first electrode.
 4. The light emitting device according toclaim 1, wherein a dielectric layer is further disposed on the steppedlight transmissive electrode, and the first electrode contacts one sideof the dielectric layer.
 5. The light emitting device according to claim4, wherein the second electrode contacts the other side of thedielectric layer.
 6. The light emitting device according to claim 4,wherein the first electrode is disposed also on a top surface of thedielectric layer.
 7. The light emitting device according to claim 4,wherein the dielectric layer is a light transmissive dielectric layer.8. The light emitting device according to claim 4, wherein thedielectric layer is disposed in a mesa edge region.
 9. A light emittingdevice comprising: a substrate; a light emitting structure comprising afirst conductive type semiconductor layer, an active layer, and a secondconductive type semiconductor layer on the substrate, the light emittingstructure exposing a portion of the first conductive type semiconductorlayer upward; a light transmissive electrode having a stepped portion onthe second conductive type semiconductor layer; a second electrode onthe light transmissive electrode; and a first electrode on the exposedfirst conductive type semiconductor layer, wherein the lighttransmissive electrode has a stepped portion between the secondelectrode and the first electrode, and the light transmissive electrodehas a thickness gradually decreasing from the second electrode towardthe first electrode.
 10. The light emitting device according to claim 9,wherein the light transmissive electrode has a gradually decreasingthickness on the mesa etching region.
 11. The light emitting deviceaccording to claim 9, wherein the light transmissive electrode has athinner thickness on the mesa etching region.
 12. The light emittingdevice according to claim 9, wherein a dielectric layer is furtherdisposed on the stepped light transmissive electrode, and the firstelectrode contacts one side of the dielectric layer.
 13. The lightemitting device according to claim 12, the second electrode contacts theother side of the dielectric layer.
 14. The light emitting deviceaccording to claim 12, wherein the first electrode is disposed also on atop surface of the dielectric layer.
 15. The light emitting deviceaccording to claim 12, wherein the dielectric layer is a lighttransmissive dielectric layer.
 16. The light emitting device accordingto claim 12, wherein the dielectric layer is disposed in a mesa edgeregion.
 17. The light emitting device according to claim 9, wherein thelight transmissive electrode is formed of at least one of ITO,IZO(In—ZnO), GZO(Ga—ZnO), AZO(Al—ZnO), AGZO(Al—GaZnO), IGZO(In—GaZnO),IrOx, RuOx, RuOx/ITO, Ni/IrOx/Au, Ni/IrOx/Au/ITO, Ni, Pt, Cr, Ti, andAg.
 18. The light emitting device according to claim 12, wherein thefirst electrode, the dielectric layer, and the second electrode functionas a capacitor.
 19. A light emitting device package comprising: apackage body; a light emitting device on the package body, the lightemitting device according to claim 1; and an electrode electricallyconnecting the package body to the light emitting device.